The Herald reports that a company representative did not return calls for comment, but XTO's report to the state Oil and Gas Conservation Commission says the spill happened when a cow inadvertently opened a valve.

Christi Zeller, executive director of the Energy Council, says she has never heard of such a thing. She says she looks at almost all the spill reports every year.

The company said about 420 gallons of "produced water" pooled on site.

Produced water refers to the wastewater byproduct of oil and gas production, which can contain high concentrations of hydrocarbons and carry negative environmental impacts.

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